High power solid state lasers often achieve high power by integrating multiple gain-modules within a common resonator thus benefiting from industrial production capability limited to lower power gain modules. Thin disk laser gain modules may be sized by commercial laser welding needs and are typically limited to 4-5 Kw single disk designs. Scaling to higher power levels is generally achieved by integrating multiple single-disk modules into a common resonator, thus achieving a power multiplier associated with the number of gain modules incorporated into the high power resonator. Multiple-gain module scaling architectures may experience problems associated with build-up of amplified spontaneous emission (ASE) within the thin-disk gain element leading to high intensities within the gain material and eventual catastrophic destruction of the crystal.
The safety of the individual crystals is dependent on a delicate balance between absorbed pump power and extracted laser power across the pumped region of the disks/crystals. When the high-power multi-gain module resonator is efficiently extracting energy from each laser crystal the individual disks/crystals are relatively safe from the ASE damage mechanism. However, if this efficient extraction is interrupted all of the disks/crystals within the high-power resonator are at risk for catastrophic failure. Various scenarios can be envisioned which may lead to interruption of efficient extraction within the high-power resonator. These may include failure of a resonator fold mirror, failure of a single gain module, since a thin disk crystal acts as a resonator mirror, dust contaminant interrupting the beam, and other events.
Many of the existing solutions are not capable of reliably shutting down the laser within a short enough time to preserve the gain-media conditions at the time of initial damage. One of the existing solutions is the incorporation of helper resonators that run concurrent with the high-power main resonator and act as a fast analog optical system to maintain efficient power extraction from the thin disks should the high-power resonator cease efficient lasing. However, this first line of defense can be compromised under potential loss-of-lasing scenarios. Damage scenarios that involve initial damage to intra-cavity optical elements within the high-power resonator can create enough optical loss within the high-power resonator to create a condition of poor extraction efficiency from the thin disk by the main resonator. Under this condition the helper resonators are designed to power up to maintain the efficient extraction from each disk. However, if the initial cause of the main resonator loss of lasing also affected helper resonators they may not achieve the necessary intra-cavity intensity fast enough to prevent additional disk/crystal destruction.
An apparatus and method is needed which may solve one or more problems of one or more of the conventional laser safety systems and/or methods of operating a laser safety system.